At the moment, the inverter in a Fiat 500e electric car has a volume of about five liters. In the Prius, it's around 5.4 liters.

That makes inverters a relatively large object that car manufacturers have to package when designing a hybrid or plug-in vehicle. Efforts to reduce that would result in the usual benefits--reduced weight and more packaging options.

For the competition, teams will have to aim for a volume of under 0.66 liters.

At the same time, competitors will have to meet a minimum power density to enter, at 3.05 kilowatts per liter.

In a regular inverter this isn't so hard to achieve--the Prius inverter has power density of 11.1 kW/L--but in the tiny units the competition hopes to encourage it could be more problematic.

Teams will have to register by September 30, 2014. From then, they'll have to submit a technical approach by next July and will be required to bring their inverters in for testing by October 21, 2015.

“We believe that inverters will become increasingly important to our economy and environment as solar PV, batteries, and similar power sources continue their rapid growth,” says Google.

"We expect that the innovations inspired by this prize will have wide applicability across these areas, increasing efficiency, driving down costs, and opening up new uses cases that we can’t imagine today."

Electric cars would certainly be among those uses--though Google also notes that its own data centers would benefit from any developments in the technology...